If you’ve ever received a mammogram report that says you have dense breasts, you may have wondered what that means for your breast cancer risk — and whether you need to do anything differently.
Breast density is a normal characteristic of breast tissue, but it can affect both your risk of developing breast cancer and how clearly a mammogram can detect it. Understanding your breast density can help you have a more informed conversation with your doctor about your overall breast cancer risk and screening needs.
“People with extremely dense breasts do have an increased risk of developing breast cancer,” said Dr. Catherine Moore, a medical oncologist who treats breast cancer patients at the Novant Health Cancer Institute - Elizabeth in Charlotte.
She emphasized, however, that breast cancer probability is based on multiple factors, including age, activity level and family history. Understanding breast density is one part of understanding the complete picture of breast cancer risk.
Schedule your screening mammogram. It's the best way to detect breast cancer early.
Why does my mammogram report mention breast density?
Federal mammography standards set by the FDA require patients to be informed of their breast density. But knowing that your breasts are dense doesn't necessarily mean you need additional screening. Your doctor will consider your breast density along with your other risk factors to determine what screening is appropriate for you.
What are dense breasts?
Breasts are made up of milk glands and ducts, fat and fibrous connective tissue. The more glands and connective tissue a woman has, the denser her breasts will be.
Radiologists classify breast density in four categories:
- A: Almost entirely fatty, the breast is almost completely made up of fat. About 1 in 10 women are in this group.
- B: Scattered density, the majority of the breast is fatty, but there are scattered areas of density; about 4 in 10 women are in this group.
- C: Heterogeneously dense, the majority of the breast is dense, with some scattered areas of nondense tissue; about 4 in 10 women are in this group.
- D: Extremely dense, nearly all of the breast tissue is dense; about 1 in 10 women are in this group.
Dense breasts are not considered abnormal, and they are not a medical condition on their own. Breast density may vary throughout a woman’s lifetime, as breasts tend to become fattier as we get older. This means breasts may become less dense with age, although some women have dense breasts at any age.
Women with a lower body mass index may have higher breast density compared to women who are obese. Women who are transgender and take feminizing hormones may also have dense breasts.
Why does breast density matter?
Having dense breasts can affect your breast cancer risk in two ways:
- Dense breast tissue appears whiter on a mammogram image, making it harder to see a breast tumor. This is known as “masking.”
- Researchers have determined that patients who fall into category D, extremely dense breasts, have about two to four times greater risk of developing breast cancer, independent of other risk factors, Moore said.
What should I do if I have dense breasts?
Moore said the first step is to keep up with regular breast cancer screenings. Novant Health recommends that women begin yearly screening mammograms at age 40. A mammogram is an X-ray image of the breast tissue that a radiologist examines to detect any abnormalities.
Based on your results, your doctor will determine whether you need additional imaging. The imaging methods your doctor recommends may include:
- Diagnostic mammogram. This is the same procedure as a screening mammogram, using X-ray technology to capture additional images of the breast tissue. Your mammogram technologist may take images of smaller locations or different angles to provide more clarity from the initial screening images. The process typically will not feel different from your screening mammogram and results are usually delivered the same day.
- Ultrasound. An ultrasound uses sound waves, rather than X-ray, to create a picture, so the images will differ from the mammogram, allowing clinicians a new view of the breast tissue. Moore said that if your doctor recommends an ultrasound in conjunction with a diagnostic mammogram, these will be completed on the same day.
- Magnetic resonance imaging (MRI). An MRI captures multiple images of the breast, which a computer then combines to create a detailed picture. A breast MRI is typically recommended for women with high breast cancer risk, who have received a breast biopsy or who have hereditary breast cancer genes.
While Moore said an annual screening mammogram is typically “more than adequate,” she said it’s still important to be aware of what's "normal" for your breasts and to call your doctor if you feel any changes or pain. Being aware of what your breasts feel and look like is important because it helps to determine what feels normal – and normal is different for everyone.
How does breast density factor into my total breast cancer risk?
Breast density is just one factor doctors take into consideration when determining a person’s breast cancer risk. Other risk factors include:
- Family history. Having a first-degree relative (mother, sister or daughter) with breast cancer almost doubles a woman’s risk of breast cancer. About 15% of women who get diagnosed with breast cancer have a family member diagnosed with it as well.
- Genetics. Overall, the average risk of a woman in the United States developing breast cancer is about 13%. Chances climb with a BRCA1 or BRCA2 gene mutation, known as the breast cancer genes. About 50 out of 100 women with a BRCA1 or BRCA2 gene mutation will get breast cancer by the time they turn 70 years old, compared to 7 out of 100 women in the general U.S. population.
- Age. Most breast cancers are diagnosed in women over age 50.
- Hormone exposure. The age at which you received your first menstrual period. Starting periods before age 12 exposes the body to hormones longer.
- Reproductive history. Having a first pregnancy after age 30, not breastfeeding, and never having a full-term pregnancy can raise breast cancer risk.
- Lifestyle. These factors include your diet, your weight, how often you exercise, how often you drink alcohol and whether you smoke.
Moore said that while breast density changes the probability of developing breast cancer, doctors look at breast cancer risk as an overall assessment, weighing the multiple risk factors. Healthy lifestyle choices, like regular exercise, can offset some risk factors.
What questions should I ask about breast density?
Moore emphasized that forming a plan for breast cancer risk assessment, screenings, diagnostics and preventive measures is a highly individualized process. There’s no one right way to do it.
Although it’s tempting to turn to “Dr. Google,” she encourages all people to put away the computer and instead have a conversation with a doctor who can take your personal history and risk factors into account, then make recommendations. Understanding your overall risk, not just one element of risk, is important.
“I think it's a matter of gathering information and gathering knowledge,” Moore said. “And the more you know about it, the more you can just make the right decisions for yourself.”
Some questions that the National Cancer Institute recommends to help you start a conversation about breast density with your doctor or advanced practice provider are:
- Are there any dense breast-related findings in my recent mammogram?
- Do you recommend additional screening or diagnostic tests for me?
- What is my overall personal risk of breast cancer, given my risk factors?
